Dust altitude and infrared optical depth from AIRS

[摘要] We show that mineral dust optical depth and altitude can be retrieved from the Aqua -Advanced Infrared Radiation Sounder (AIRS) measurements. Sensitivity studiesperformed with a high spectral resolution radiative transfer code show that dust effect on brightness temperatures may reach about 10 Kelvins for some channels.Using a Look-Up-Table approach, we retrieve not only the 10 µm optical depth but also the altitudeof Saharan dust layer, above the Atlantic Ocean, from April to September 2003.A key point ofour method is its ability to retrieve dust altitude from satellite observations.The time and space distribution of the optical depth is in good agreement withthe Moderate resolution Imaging Spectroradiometer (MODIS) products. ComparingMODIS and AIRS aerosol optical depths, we find that the ratio between infraredand visible optical depths decreases during transport from 0.35 to 0.22,revealing a loss in coarse particles caused by gravitational settling. The evolution ofdust altitude from spring to summer is in agreement with current knowledge on transport seasonality.

[学科分类] 大气科学